Cosmetic: Fix a number of typos, no functional changes.

Fix various misspellings of things like "environment", "kernel",
"default" and "volatile", and throw in a couple grammar fixes.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
diff --git a/board/RPXlite_dw/README b/board/RPXlite_dw/README
index 14296b2..9e2d0f4 100644
--- a/board/RPXlite_dw/README
+++ b/board/RPXlite_dw/README
@@ -87,9 +87,9 @@
 
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-A word on the U-Boot enviroment variable setting and usage :
+A word on the U-Boot environment variable setting and usage :
 
-In the beginning, you could just need very simple defult environment variable setting,
+In the beginning, you could just need very simple default environment variable setting,
 like[include/configs/RPXlite.h] :
 
 #define CONFIG_BOOTCOMMAND                                                      \
diff --git a/board/freescale/mx28evk/README b/board/freescale/mx28evk/README
index 524f3fc..0389a1d 100644
--- a/board/freescale/mx28evk/README
+++ b/board/freescale/mx28evk/README
@@ -29,11 +29,11 @@
 
 There are two targets for mx28evk:
 
-"make mx28evk_config"		- store enviroment variables into MMC
+"make mx28evk_config"		- store environment variables into MMC
 
 or
 
-"make mx28evk_nand_config"	- store enviroment variables into NAND flash
+"make mx28evk_nand_config"	- store environment variables into NAND flash
 
 Choose the target accordingly.
 
diff --git a/board/sbc8349/README b/board/sbc8349/README
index 2c35919..e2d60cc 100644
--- a/board/sbc8349/README
+++ b/board/sbc8349/README
@@ -50,7 +50,7 @@
     trying to preserve your old environment settings and user flash).
   - Set the start address of the erase/flash process to FF80_0000
   - Set the target RAM required to 64kB.
-  - Select sectors for erasing (see note on enviroment below)
+  - Select sectors for erasing (see note on environment below)
   - Select Erase and Reprogram.
 
 Note that some versions of the register files used with Workbench